Ok, so it's now technically possible for a Fleet to cancel a mission. Please allow this for any project, for both fleets, and especially for personal Rep systems.

Yes, please! I have myself queued the wrong item for a Rep mission, and I'd be happy to lose the few things I put into it before I noticed just to be able to free the slot back up. Being forced to pay 30k+ dil for something I don't want to free the slot is lame at best.